I'm a Customer Service Agent for a governmental assistance agency. We often have situations where clients numbers have changed, and someone else has been assigned the old number.
When I want to make a note to my supervisor that the person I've reached is not the client and that the 'person I've reached' has requested in very virile, flammable language that they would like us to remove their number from our calling list/dB, it vexes me that all I can come up with is "the answerer," which sounds dumb, and "the number's new owner…"
Best Answer
callee (if you want to go with a single word)
Though this term is usually used in computing.
There is also called party which is more related to your context.